That file has really screwed up timestamps, just from the start: (the pattern holds)
Frame, rtStart: 0, dur: 200000, diff: 0, key: 1, type: I, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 400111, dur: 200000, diff: 400111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 400000, dur: 200000, diff: -111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 600000, dur: 200000, diff: 200000, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 800000, dur: 200000, diff: 200000, key: 0, type: P, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 1200111, dur: 200000, diff: 400111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 1200000, dur: 200000, diff: -111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 1400000, dur: 200000, diff: 200000, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 1600000, dur: 200000, diff: 200000, key: 0, type: P, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 2000111, dur: 200000, diff: 400111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 2000000, dur: 200000, diff: -111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 2200000, dur: 200000, diff: 200000, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 2400000, dur: 200000, diff: 200000, key: 0, type: P, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 2800111, dur: 200000, diff: 400111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 2800000, dur: 200000, diff: -111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 3000000, dur: 200000, diff: 200000, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 3200000, dur: 200000, diff: 200000, key: 0, type: P, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 3600111, dur: 200000, diff: 400111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
Frame, rtStart: 3600000, dur: 200000, diff: -111, key: 0, type: B, repeat: 0, interlaced: 0, tff: 0
The duration is constant 20ms (50 FPS), but the frame timestamps are in a rather weird pattern, and even going backwards (even if only by 11.1 microseconds). Those backwards frames are being dropped by JRVR, hence the lower FPS, and the not-smooth presentation. I'm not sure yet if the file is screwed up or there is an issue in the demuxer, but thats what JRVR gets in any case.
To help with diagnosing frame pacing issues in JRVR, I'll add an additional logging function for frame timings in particular, which will not be tied to the main MC log, since it will be extremely verbose, and needs to be separately enabled as well as logging to a different file (similar to the TV log, i guess).